The present invention relates to a displacement control valve controlling the discharge capacity of variable displacement compressors that are included in the refrigerant circuit of air conditioners.
A typical control valve incorporates a solenoid valve, which is externally controllable. FIG. 4 shows an example of an electromagnetic actuator portion 101 in the control valve. A retainer cylinder 102 having a bottom portion is disposed in the electromagnetic actuator portion 101. A stationary core 103 and a movable core (plunger) 104 are disposed in the retainer cylinder 102. A coil 105 is disposed at outside of the retainer cylinder 102. Electric current through the coil 105 generates electromagnetic force between stationary core 103 and movable core 104. The electromagnetic force is applied to the movable core 104 to slide along an inner cylindrical surface of the retainer cylinder 102. This movement is transmitted to a valve body (not shown in the drawing) through a rod 106. The displacement of valve body based on the movable core 104 serves to adjust the opening degree of the valve to control a discharge displacement of the compressor.
The discharge displacement is achieved by, for example, changing a pressure in a crank chamber in which a swash plate is disposed. To change the pressure in the crank chamber, the control valve regulates the degree of the opening in a pressurizing passage, which supplies a pressurized refrigerant gas from the discharge chamber to the crank chamber.
Recently, air conditioners utilizing carbon dioxide as a refrigerant gas has become generally used. In such system, the pressure of the refrigerant gas is much higher than that of a conventional CFC (chlorofluorocarbon) gas. Accordingly, in order to control the displacement of the compressor that deal with carbon dioxide, it is necessary to increase the withstanding pressure of the control valve as well as the compressor. For example, a cylindrical wall of the retainer cylinder 102 may be thick to resist the internal pressure.
However, the retainer cylinder 102 is made of non-magnetic material to prevent magnetic flux from leaking out between the stationary core 103 and the movable core 104. Therefore, if the wall of the retainer cylinder 102 is thickened to resist the high internal pressure sufficiently, it will be harder for the magnetic flux to go through between the coil 105 and the movable core 104.
Accordingly, an object of the present invention is to provide a control valve, especially control valve in variable displacement compressor, in which a magnetic flux can easily go through between a coil and movable core even if a wall of the retainer cylinder is thickened in order to increase its withstanding pressure.
Another objective of the present invention is a method of adjusting the tolerance of the movable extent in the control valve, which is caused during its manufacture.
To achieve the foregoing, the present invention provides a control valve for operating fluid flow that goes through the control valve. The control valve includes a retainer cylinder, a stationary core, a movable core, a shim, a coil and a valve body. The retainer cylinder includes a first cylindrical member made of non-magnetic material and a second cylindrical member made of magnetic material, the second cylindrical member having a bottom portion. The stationary core is disposed in the retainer cylinder. The movable core is disposed in the retainer cylinder, and located between the stationary core and the bottom portion of the second cylindrical member. The shim is made of non-magnetic material, and disposed in the retainer cylinder and located between the movable core and the bottom portion of second cylindrical member. The coil is disposed around the retainer cylinder. The valve body is movably linked with the movable core. The valve body is actuated by a movement of the movable core in an elongated direction of the retainer cylinder. The movement of the movable core is based on an electromagnetic force that is generated between the stationary core and the movable core in accordance with an electric current supplied to the coil.
The control valve is appropriate for a variable displacement compressor that adjusts the discharge displacement in accordance with the inclination of a drive plate located in a crank chamber.
Also, the present invention provides a method of adjusting the amount of movable extent of a movable core in a control valve for operating fluid flow that goes through the control valve including a step of adjusting a thickness of the shim so that the amount of movable extent of the movable core in the retainer cylinder is adjusted.
Regarding the description of the invention, the term of xe2x80x9cbottomxe2x80x9d refers to a relative location with respect to the other structural elements described below, and is illustrated, by way of example, in FIG. 2. Therefore, if the control valve of the invention is installed in practical use xe2x80x9cupside downxe2x80x9d with respect to the orientation depicted in FIGS. 1-3, the term xe2x80x9cbottomxe2x80x9d should mean the reverse as